The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Wireless communication systems such as 3G and long term evolution (LTE) communication systems rely on feedback and control of a transmit power of signals transmitted between wireless devices. For example, the transmit power may vary due to variations in components of the wireless devices (e.g., mobile phones, tablets, laptop computers, etc.), the wireless communication channel, interference from other electronic devices, and/or other factors. A wireless device transmitting a signal may monitor characteristics of the transmitted signal to adjust the transmit power accordingly.
FIG. 1 shows an example wireless communication device 100 operating in a 3G/LTE wireless communication system. The wireless communication device 100 includes a transmitter 104, a receiver 108, a directional coupler 112, and an antenna 116. The transmitter 104 receives a transmit signal to be transmitted via the antenna 116. For example, the transmitter 104 receives a baseband transmit signal and modulates a radio frequency (RF) carrier based on the baseband transmit signal for transmission as an RF signal via the antenna 116. The receiver 108 receives RF signals via the antenna 116 and converts the RF signals to corresponding receive signals (e.g., baseband receive signals).
The transmitter 104 generates the modulated RF carrier at a desired transit power level. For example, the transmit power level may correspond to a target power level received by the transmitter 104. The transmitter 104 provides the modulated RF carrier to the antenna 116 through the directional coupler 112. The directional coupler 112 couples signals transmitted by the transmitter 104 to the receiver 108. Accordingly, various characteristics of signals transmitted from the transmitter 104 to the antenna 116 through the directional coupler 112 are detectable by the receiver 108. For example, the receiver 108 may detect the transmit power level of the signals transmitted from the transmitter 104 to the antenna 116 based on the coupled signals.
FIGS. 2A and 2B show example directional couplers configured to couple transmitted signals to one or more coupled ports (e.g., a port in communication with a receiver). FIG. 2A shows a uni-directional coupler 200 having an input port 204, an output port 208, a coupled port 212, and a terminated port 216. The input port 204 receives a transmit signal (e.g., from a transmitter) and outputs the transmit signal (e.g., to an antenna) via the output port 208 on a transmit line 220. The transmit line 220 is coupled to a coupling line 224. Accordingly, signals transmitted via the transmit line 220 are coupled (e.g., forward coupled) to the coupling line 224, and characteristics of the signals transmitted via the transmit line 220 are detectable via the coupled port 212.
FIG. 2B shows a bi-directional coupler 228 having an input port 232, an output port 236, a coupled port 240, and an isolated (coupled) port 244. The input port 232 receives a transmit signal and outputs the transmit signal via the output port 236 on a transmit line 248. The transmit line 248 is coupled to a coupling line 252. Accordingly, signals transmitted via the transmit line 248 are coupled (e.g., forward coupled) to the coupling line 252, and characteristics of the signals transmitted via the transmit line 248 are detectable via the coupled port 240. Conversely, any signals incidentally received on the transmit line 248 (e.g., from the antenna) are detectable via the isolated port 244.
FIGS. 3A and 3B show example dual-directional couplers configured to couple transmitted signals to one or more coupled ports. FIG. 3A shows a dual-directional coupler 300 in a series arrangement. The dual-directional coupler 300 includes an input port 304, an output port 308, a forward coupled port 312, a reverse coupled port 316, and terminated ports 320 and 324. The input port 304 receives a transmit signal and outputs the transmit signal via the output port 308 on a transmit line including transmit line portions 328 and 332. The transmit line portion 328 is forward coupled to a coupling line 336 and the transmit line portion 332 is reverse coupled to a coupling line 340. Accordingly, signals on the transmit line portion 328 are forward coupled to the coupling line 336, and characteristics of the signals are detectable via the coupled port 312. Conversely, signals on the transmit line portion 332 are reverse coupled to the coupling line 336, and characteristics of the signals are detectable via the coupled port 316.
FIG. 3B shows a dual-directional coupler 344 in a parallel arrangement. The dual-directional coupler 344 includes an input port 348, an output port 352, a forward coupled port 356, a reverse coupled port 360, and terminated ports 364 and 368. The input port 348 receives a transmit signal and outputs the transmit signal via the output port 352 on a transmit line 372. The transmit line 372 is forward coupled to a coupling line 376 and reverse coupled to a coupling line 380. Accordingly, signals on the transmit line 372 are forward coupled to the coupling line 376, and characteristics of the signals are detectable via the coupled port 356. Conversely, signals on the transmit line 380 are reverse coupled to the coupling line 380, and characteristics of the signals are detectable via the coupled port 360.